Title says all, what the biggest challenge you've had to overcome in your life? It can be anything, video games, sports, life events, whatever comes to mind. Recently my biggest challenge was to bike 40 miles and I managed to do it today ^^

When I was 15, I completed a marathon with no training, Basically one morning, I woke up and just ran...I mostly just ran then walked, rinse and repeated the whole length..
I can't remember the exact distance, I'm fairly certain it was 10-15 kilometres. In the end, I moved up about 30 spots. So considering I never thought I'd make it even half way, I actually did a lot better than I thought I ever could.

Did a belt test at my dojo that lasted 6 hours. People cried, people threw up, people broke down. But those who didn't found surprising strength to keep going. It was really an eye-opener for me. That was the day I somehow managed to do 100 pushups at once, had to fend off 10 people blindfolded (they were in a circle around me and the instructor would make random people attack me from any direction and I would have to react), sparred 5 different people in succession for 3 minutes each with no breaks, and held a sandbag over my head in a painful position for half an hour. That belt felt earned.